Observation: The Poisson distribution can be approximated by the normal distribution, as shown in the following theorem. For Poisson, the mean and the variance are both $\lambda$. Please follow the link below for details. What would be the average be? (It is more general though, so I like recommending that approach as well. *where the mean is 5.3, Hello Brianna, The paper by Patil and Kulkarni discusses 19 different ways to calculate a confidence interval for the mean of a Poisson distribution. Kasper Langmann, Co-founder of Spreadsheeto If the average is 100 and the confidence value is 10, that means the confidence interval is 100 ± 10 or 90 – 110. Here your mean is 1451.45. A fire brigade A is on average called out 5 times a day. Lena, If you are using the Kolmogorov-Smirnov test, then D > D-crit means that data does not come from a Poisson distribution. The average number of signals sent from a station is 3 per day which do not reach properly to the another station . In the finance community, an audit sampling method (monetary unit method) is using a confidence factor published by the American Institute of Certified Public Accountants. what is the probability that I will have at least a hundred people signed up at once? Eugene, If however you want to know the probability that you will have say m errors in the month (instead of the average number), then you can use the approach described on the referenced webpage. The number of hit can be addressed simultaneously on website is 35K and the average hit per min is 15K. Note that in many cases, the licenses checked out one hour is the same licenses check out by the same person in a previous hour(the license continues to be check out by the same user over multiple hours or days). This is an advantage since there is a tendency for count data to be skewed to the right. (binomial, poisson and normal). there is a Poisson process), then you should be ok. One quick check to see whether data follows a Poisson process is to see whether the mean is roughly equal to the variance (as described on the website). Any help would be greatly appreciated. 307692 5 4.414 Instead, you can use the following function provided by the Real Statistics Resource Pack. Eugene. 4. as for #2 except that it is not the same exact test but a standard test that is supposed to measure the same thing (such as the SAT)? Normal: It really depends on how you are going to use n since NORMDIST doesn’t directly use n. Many thanks for the explanation, i’m trying to find a way to apply this to sports betting using Excel, i’ve managed to locate a Poisson template and i’m wondering if there are any know ways of viewing football prediction results, I don’t know any way of applying this to sports betting, but perhaps someone else in the community can help. Ainul, Recently my team assignment selected Hotel beds unoccupied with 50 counts and our expected number=mean= lambda. checking out of licenses) that follows a Poisson distribution, but you haven’t said anything about the “service time” (i.e. for how long the license is checked out). But @Travis "would like to know how confident I can be in my $\lambda$", so it should be a confidence interval around the sample mean. Confidence Intervals for the Mean of a Poisson Distribution "Exact" 95% Confidence Intervals. confidence interval for a Poisson mean such as Cai , Byrne and Kabaila , Guan , Krishnamoorthy and Peng , Stamey and Hamillton , Swifi  and others. 228 A sample of 32 hotels show that the mean of numbers of guests is 55, and I would like to find a P(100<=x<=150), is it correct my formula is =POISSON(150,55,TRUE)-POISSON(99,55,TRUE) ? Charles. I wonder if it would be correct to use poisson distribution to determine safety stock for a product when the product has the following demand pattern for the last 12 months: 3 580 Hope you can assist me in this matter. Lena, The AICPA has disclosed that these statistical tables are based on poisson distribution. Making statements based on opinion; back them up with references or personal experience. POISSON(x, μ, FALSE) = probability density function value f(x) at the value x for the Poisson distribution with mean μ. POISSON(x, μ, TRUE) = cumulative probability distribution function F(x) at the value x for the Poisson distribution with mean μ. I have just updated the Chi-square Goodness of Fit webpage with a test to determine whether data conforms to the Poisson distribution.